Multiple lock systems are used to allow access to an area by multiple users while preventing access to unauthorized persons. Such systems may be used, for example, on property with oil and gas leases, hunting leases, or wireless communications towers. One advantage of multiple lock systems over a single lock system is that a user authorized to access multiple areas may use locks with the same key for each area, eliminating the need for that user to carry multiple keys and reducing confusion over which key provides access to which area. Another advantage is that when a user is no longer authorized to access the area, the user's lock can be replaced or eliminated, and the distribution of new keys to all of the other users is not required.
One simple prior known multiple lock system uses a chain around a gatepost and gate secured by multiple padlocks linked in series with each user having their own padlock and key. One disadvantage of this system is that a user may bypass one or more locks when resecuring the chain, thereby preventing access to the users of the bypassed locks. The padlocks are also vulnerable to being forced or cut open. Detection of an unauthorized lock, added by cutting the chain and inserting the lock, is very difficult with this system.
U.S. Pat. No. 2,707,125 to Ritter discloses a tubular multiple padlock system that mounts on a gatepost. U.S. Pat. No. 3,889,497 to Tuttle discloses a plate type multiple padlock -device where-padlocks must be used in multiples of four. U.S. Pat. No. 3,988,031 to Meyer and U.S. Pat. No. 4,997,219 to Carter disclose vertical wheel type multiple padlock devices where removal of a peripheral padlock provides access to a hole that allows retraction of a locking bar. U.S. Pat. No. 4,697,443 to Hillin discloses a horizontal wheel type multiple padlock device having radial access-channels with a fastening gate for each padlock. Each of the above patented devices has a predetermined number of positions for padlocks and none can be reconfigured as the number of users changes.
U.S. Pat. No. 5,868,015 to Eaker discloses a multiple padlock system with a locking bar and a plurality of coupling segments. Segments can be added or removed if the number of users changes. The number of segments cannot be controlled by a master user since any authorized user could add a segment. When a user is no longer authorized, that user's padlock and at least one segment must be removed to reconfigure the system. Such a reconfiguration requires coordination with one of the users adjacent to the user that is being removed, in order to remove the segment. In each of the above listed devices the padlocks are vulnerable to boltcutters or a sledgehammer.
Accordingly, there is a need for a multiple padlock system that can be readily reconfigured, without the coordination of several current users, as the number of users changes. A master user should be able to control the reconfiguration. The multiple lock system should also protect the padlocks from boltcutters and sledgehammers.